It has been proposed to provide an air-bag which has a plurality of inflatable regions or chambers which are to be supplied with gas from a gas generator. One example of such an air-bag is a so-called “inflatable curtain” which is adapted to be mounted in the roof of the vehicle above the door openings of the vehicle, and is also adapted, when an accident occurs, to be deployed to lie adjacent the window openings formed in the door, thus forming a protective curtain located between the occupant of the vehicle and the side of the vehicle. Such inflatable curtains provide protection to the occupant of the vehicle in the event of a side impact or roll-over situation.
U.S. Pat. No. 6,199,898 B discloses a safety device of this type in which the inflatable curtain is formed of an inflatable element which is divided into a plurality of regions or chambers which are to be inflated. An internal fabric gas supply duct is provided. That gas supply duct is provided, along its length, with circular apertures formed in the wall of the duct through which gas can flow from the duct into those regions or chambers of the inflatable element which are to be inflated.
It is conventional for the main fabric parts of the air-bag, and also the internal gas supply duct, to be cut-out from a large sheet or roll of fabric in such a way that maximum use is made of the fabric so that there is minimum wastage. The internal fabric gas supply duct is normally formed by taking an elongate strip of fabric and folding it so that the opposed edges are brought together, those opposed edges being inserted between the adjacent edges of the layers of fabric which form the main part of the inflatable curtain. The four super-imposed edges are stitched together.
Depending upon the cutting-out pattern used for cutting the main fabric parts of the air-bag and the supply duct from the sheet or roll of fabric, the axis of the gas supply duct may effectively make any angle with the warp and weft yarns of the fabric. The axis of the fabric element forming the gas supply duct may, for example, be aligned with either the warp yarns or the weft yarns. In such a case it has been found that the textile “tube” that constitutes the gas supply duct may be almost non-flexible in a radial direction. Consequently the edges of the circular apertures formed in the gas supply duct may “tear” during the inflation process. This may cause an irregular deployment of the inflatable curtain.
If the axis of the element that forms the gas supply duct is such that the warp and weft yarns each make an angle of, say, 45° to the axis, the resultant “tube” may be quite flexible in the radial direction. However, during inflation, the region of fabric around the outlets may deform or may become very substantially “frayed” or with some of the fibres forming the fabric extending into the regions or chambers which are to be inflated. If the internal gas supply duct is not located in exactly the correct position within the inflatable curtain, this deformation of the region around the apertures may be blocked, for example by the dividing seam between two adjacent regions or chambers. Again, in this case, the deployment of the inflatable curtain may be irregular.
The present invention seeks to provide an improved air-bag.